A conventional technique of energy pattern scanning employs a raster-scan format analogous to the usual scanning of a television screen. The line/frame raster scan format is widely used for its compatibility with two-dimensional detector arrays such as charged-coupled-device (CCD) type; however there are a number of inherent drawbacks and disadvantages. Elaborate gating techniques are required, for example to handle line and frame rate retrace. Simple image rotation presents complex and time-consuming processing tasks to the operating hardware and software. The scanned field is inherently square or rectangular although the region of interest is more likely to be circular, thus scanning the corner regions generally represents wasted or low-yield effort. Furthermore, with raster scan, the resolution is inherently constant over the entire scanned region, although in a great deal of actual practice, the requirement for resolution increases strongly toward the center of the region where target acquisition activity tends to concentrate; for this reason, one raster scan approach of known art provides "super-scan", an auxiliary system for effectively increasing the scanning density by a factor of several times over a small region in the center of the field of view, for enhancing target acquisition and tracking resolution. Such a two-step (or multi-step) system imposes burdens of complexity in hardware and supporting software.
Polar scanning offers an attractive alternative from several viewpoints including increased center resolution, continuous scanning progression without discontinuity, and inherent ease of data processing, e.g. data interpretation relating to simple rotation.